by William M. Welch, USA TODAY

by William M. Welch, USA TODAY

LAS VEGAS - With a barrage of attack ads that confront TV viewers around the clock, rookie Republican Sen. Dean Heller is trying to hold his seat against a similarly negative video assault from his challenger in a race that has put Nevada at the center of the struggle over Senate control.

Heller, 52, appointed to the seat when his GOP predecessor resigned after an affair and an ethics investigation, has relentlessly attacked Democratic Rep. Shelley Berkley as an ethics-challenged tool of House Speaker Nancy Pelosi as she tries to move up to the Senate after seven terms as a congresswoman.

Berkley, 61, dismisses the ethics charges as tame stuff by Las Vegas' Sin City standards. She is relying on President Obama's power to turn out Democrats, especially Latino voters, to lift her in this fast-growing but economically hard-hit state. She ties Heller to GOP presidential candidate Mitt Romney and charges he would "gut" education and end Medicare's guarantee of health care for seniors.

The result is a cacophony of unpleasant TV viewing - fueled by more than $20 million from political committees, unions and other outside groups - that has driven up both candidates' unfavorable ratings. "It's two unlikeable candidates running highly negative campaigns," says David Damore, political scientist at the University of Nevada-Las Vegas.

Both sides are spending heavily to try to break through to Nevada voters who have found their state playing an outsized role in 2012 politics.

Democrats switched Nevada to blue in 2008 when Obama won handily here, and they stunned Republicans two years later when Senate Majority Leader Harry Reid won re-election by 6 percentage points against a Tea Party-backed GOP candidate despite polls suggesting Reid was well behind. Heller, like Romney and Reid, is Mormon, and Mormons make up 6% of Nevada's population.

Republicans think there's plenty of reason they should win Nevada, where the housing collapse hit hard and unemployment, at 11.8%, is the highest in the nation. But changing demographics with a

Obama has a small lead here in recent polling here, and the president runs ahead of Berkley in most surveys. She is relying on Reid's political organization to give her a lift.

"This is probably the bluest purple state in the country," says Heller's campaign manager, Mac Abrams, explaining the party's challenge this year in Nevada.

Repeated visits by Romney and Obama have given Heller and Berkley the opportunity to appear before large crowds, but most of the campaigning is being done on airwaves.

In one of his few recent public appearances, Heller touted Romney before a large, mostly white crowd in suburban Henderson, boasting that the GOP nominee would create 14 million jobs as president - 2 million more than Romney promised moments later. "I have an opponent who votes with Pelosi 97% of the time," Heller said, without explaining that Pelosi is minority leader of the U.S. House.

He drew cheers for promising not to raise taxes, to back building the Keystone oil pipeline and to repeal Obama's health care law.

A day later, before a large and ethnically diverse crowd that turned out to see Obama in North Las Vegas, Berkley charged that the Republican candidates would "shred the guarantee of Social Security and Medicare," slash education spending and set back women's efforts to receive pay equality with men. "Romney and Heller want to take us back to the 1950s," she said.

Heller has held a small lead in most independent polls. The RealClearPolitics.com average of polls has Heller ahead by 3.5 percentage points, while it shows Obama ahead in the state 50%-47.6%.

The seat has been in GOP hands for years. Heller was appointed to it last year after GOP Sen. John Ensign resigned. So it represents a rare opportunity for Democrats to take a seat from Republicans in the fight to protect a narrow Senate majority.

"This is offense," says Matt Canter, communications director of the Democratic Senatorial Campaign Committee. "The Republicans pretended that they had put this one away, but they have not. The demographics remain extremely difficult for them. ... It's a tossup race."

With 1.2 million registered voters in Nevada, Democrats enjoy an advantage of 90,000. Berkley represents parts of Las Vegas and Clark County, where almost three-quarters of Nevada's voters live. Heller is from Carson City in the more GOP-leaning northern part of the state.

More than a quarter of Nevada's population is Latino, and that figure approaches 30% in the Las Vegas area. Damore, the political scientist, says Heller's record makes it tough for him to attract those voters.

Heller opposed Democratic efforts to overhaul immigration laws, calling the Dream Act amnesty, and he opposed Obama's order halting deportations and providing temporary residency to some young undocumented immigrants. He supported Arizona's tough immigration law that has become a flashpoint for Latino groups, and he backed legislation designating English the country's official language. He has backed a constitutional amendment to end birthright citizenship, meaning children born in this country to illegal immigrants would no longer get automatic citizenship.

But Heller distanced himself from some of Romney's most controversial remarks, such as the videotaped speech in which Romney said 47% of voters are dependent on government and beyond his reach as a candidate.

"He has found it very difficult to differentiate himself from Mitt Romney among Latino voters," Canter said. "He needs to win a larger share of Latinos if he's going to win."

Heller, a former stockbroker and state legislator who was elected three times to the House before being appointed to the Senate by the Republican governor, has focused his campaign on attacking Berkley. His ads call her the most corrupt member of Congress. He points to a House ethics investigation into whether Berkley used her position to improperly benefit her physician husband by intervening with Medicare officials to keep open a kidney transplant center.

"Everything that's wrong with Congress," a Heller ad says of Berkley.

Berkley, an attorney and former casino executive, denies the charges. She hopes voters are looking beyond that issue and are tuning out the negative barrage.

"This is politics in 2012," she says. "I don't think people are listening to the negative attacks."

Some are listening, though.

Andrew Moreno, 71, a casino card dealer and Latino voter who showed up for Romney's latest rally, said he backs Heller because his party "wants to cut taxes" and cited Berkley's ethics investigation

Darrian Griffin, 41, a former Marine and veteran of the Gulf War, brought his family to Obama's recent rally but paused when asked if he and his wife, Dolphina, would vote for Berkley. Citing ads attacking Berkley on ethics and for flipping foreclosed homes for profit, he said, "That's a tough cookie. ... She may lose votes for that."

But at the East Las Vegas Community Center, an early-voting place for the largely Latino and black neighborhoods there, Camille Franklin says Obama voters will go with Berkley: "I think she'll do fine."